BIOB50H3 Chapter Notes - Chapter L#19: Palearctic Realm, Krakatoa, Main Source
LECTURE#19, pages 400-420
CHAPTER 18: BIOGEOGRAPHY
BIOGEOGRAPHY AND SPATIAL SCALE (18.1)
-Biogeography: variation in species
composition and diversity among
geographic locations
- See a latitudinal gradient in terms of
species diversity
- Roughly 90% of species in new zealnd are
endemic: occur nowhere else on earth
The North Island of NZ is
warmer and has more
diverse forests w/ lots of
flowering tree species and
few conifers, the South
Island has 100 more tree
species than north
1. Species richenss and
composition vary w/ latitudes
(lower tropical latitudes have
many more/different species
than at higher latitudes)
2. Species richness and
composition vary from
continent to continent, even
where latitude/longitude are
roughly similar
3. The same comm. Types or
biome can vary in species
richness and composition depending on its location on Earth
Patterns of species diversity at different spatial scale are interconnected
-Global scale: includes the entire world w/ major variations w/ changes in
latitude/longitude and species can be isolated from eachother
-Regional scale: encompasses smaller geographic areas in which the climate is roughly
uniform and to which species are restricted by dispersal limitation
All these species in the region are known as the regional species pool (sometimes
called the gamma diversity of the region)
Physical geography of region (eg. Number/area/distance from one another i.e
landscape) is critical to biogeography
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Species comp. and diversity vary w/I a region
dep. On how the landscape shapes the rate of
extinction in local habitats
- Within region biogeography is considered in two
ways (2 connections)
Local scale: a community species physiology
and interactions w/ other species influence
species div. at the local scale (alpha diversity)
2nd connection between the local and regional
scales of species diversity is measured by beta
diversity: tells us about the change in species
diversity and composition (the turnover of
species) as one moves from one comm. To
another across the landscape
Local and regional processes interact to determine local
species diversity
-Is local species richness also determined by local
conditions, including species interactions and the physical env?
Plot the local species richness for a comm. Against the regional species richness for
that comm.
o3 basic types of relationships are then found
1. If local species richness and regional species richness are equal
(slope =1), then all the species w/I a region will be found in the
comm. Of that region don’t find this pattern in the world
2. If local species richness is similarly proportion to regional species
richness (but relationship is not 1:1), then we can assume that local
species richness is largely determined by the regional species pool
(w/o local processes like
species interactions playing
a minor role)
3. If local species richness
levels off despite an
increasing regional species
pool, then local processes
can be assumed to limit
local species richness
-Witman study: looked at relationship for
marine invertebrate comm. Living on subtidal
rock walls at a variety of locations throughout
the world
Looked at 49 sites in 12 regions and
surveyed species richness n rock walls at
10-15m water depth compared these values w/ the regional species richness
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values from published lists of invert. Species capable of living on hard substrates at
similar depth a plot of local vs regional at all the sites should that local species
richness was always proportionally lower than regional species richness
Local species richness also never levelled off (i.e comm. Didn’t become saturated) at
high regional richness values thus: the results of this study suggest that regional
species pools largely determine the # of species present in these marine
invertebrate comm.
-However: lack of saturation does not mean the local processes are unimportant 1.
Still unexplained variation among local comm. Regions // 2. Effects of species
interactions are highly sensitive to the local spatial scale chosen
GLOBAL BIOGEOGRAPHY (18.2)
- Alfred Russell Wallace was father of biogeography
Discovered: mammals of the Philippines were more similar to those of Africa, than
they were to those of New Guinea was called the Wallace Line
- His book revealed 2 important global patterns
Earth land masses can be divided into 6 recognizable biogeographic regions
containing distinct biotas that differ
markedly in species composition and
diversity
There is a gradient of species diversity
w/ latitude; species diversity is
greatest in the tropics and decreases
toward the poles
The biotas of biogeographic regions reflect
evolutionary isolation
- The 6 regions are the: Neartic (North
America), Neotropical (Central and South
America), Palearctic (Europe and parts of
Asia/Africa), Ethiopian (most of Africa),
Oriental (india, China and southeast Asia),
and Australasian (Australia, indo-pacific, New Zealand) these regions coincide w/
Earth’s tectonic plates
-Continental drift: scientist hypothesis that continents
drifted over Earth’s surface
- There are 3 major types of boundaries between tectonic
plates
Mid-ocean ridges: molten rock flows out of the
seams between plates and cools, creating new crust
and forcing the plates apart in a process called
seafloor spreading
Subduction zones: areas where 2 plates meet, one
plate is forced downward under another plates
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Document Summary
Biogeography: variation in species composition and diversity among geographic locations. See a latitudinal gradient in terms of species diversity. Roughly 90% of species in new zealnd are endemic: occur nowhere else on earth. The north island of nz is warmer and has more diverse forests w/ lots of flowering tree species and few conifers, the south. Types or biome can vary in species richness and composition depending on its location on earth. Patterns of species diversity at different spatial scale are interconnected. Global scale: includes the entire world w/ major variations w/ changes in latitude/longitude and species can be isolated from eachother. Regional scale: encompasses smaller geographic areas in which the climate is roughly uniform and to which species are restricted by dispersal limitation. All these species in the region are known as the regional species pool (sometimes called the gamma diversity of the region) Physical geography of region (eg. number/area/distance from one another i. e landscape) is critical to biogeography.
